✦ LIBER ✦
Unexpected regiochemistry in the reaction of some γ-trimethylsilylated 3-dialkylamino-crotonate esters with carbonyl electrophiles.
✍ Scribed by T.H. Chan; G.J. Kang
- Publisher
- Elsevier Science
- Year
- 1982
- Tongue
- French
- Weight
- 216 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
4-T'rimethylsilyl-3-dialkylaminocrotonate esters (4) react with a nwnber of carbonyl electrophiles and titanium tetrachloride to give Froducts with substitution at y-position. A dynamic equilibriwn of 4 and its O-sily'l isomer IS is proposed to explain the regiochemistry.
Compounds 4 were prepared by the following procedures:
To a solution of lithium diisopropylamide (24 mm011 in 50 ml THF containing tetramethylethylenediamine (3.2 ml) at -78'-', methyl 3-dialkylaminocrotonate (~3, 20 mmol) was added.
The mixture was stirred for 0.5 h, and then quenched with trimethylchlorosilane. Work up by the usual procedure gave 4 in 90% 1 yield of > 95% purity by H NWB.
They could be distilled in vacua without decomposition.